1. Field of the Invention
The invention relates to a method of writing information in a bit-serial sequence into consecutively arranged sectors of a record carrier body, the information written being read directly after writing for the purpose of verification and being rewritten into a subsequent sector if the information has been incorrectly written; in each sector to be inscribed there being written an identifier adjacent the information. The invention also relates to a method of reading information written in accordance with the above method. Finally, the invention relates to a device for performing the above methods.
2. Description of the Prior Art
A method of this kind is known from the article "Tape defect bypass mechanism" by N. K. Ouchi, published in IBM Technical Disclosure Bulletin, Vol. 18, No. 5, page 1577, October 1975. This article describes a method where the information originating from a data stream is written on a magnetic tape in the form of data blocks. If the verification directly after the write operation reveals that the data block has been incorrectly written, the same data block is written again in the subsequent sector. To this end, the data block to be written is stored in a buffer during writing. A sequence identifier is appended to each block to be written. This identifier does not form part of the information written by a user and indicates the logic sequence of the data blocks written. The identifier provides as if it were a sequence number for successive data blocks formed from the data stream. If a data block is written again in a subsequent sector as a consequence of the verification, the rewritten data block has the same identifier as the original data block. It is only when a next data block is fetched from the data stream that a next identifier is assigned thereto. Because the sequence of the data blocks is known, any rewritten data blocks can be recognized when the information written is read. If two or more successive data blocks have the same identifier, the data blocks have evidently been rewritten.
However, it is a drawback of such a method that correctly written data blocks are not unambiguously indicated by the identifier. When the data blocks are read, the best one of the set of data blocks having the same identifier is then selected. Furthermore, a problem is encountered if not all identifiers assigned per record carrier body are unique. If they are not unique, loss of data is still feasible. Moreover, very accurate recordkeeping of the identifiers thus selected is required if the record carrier body has not been completely inscribed.